1. Field of the Invention
The present invention relates to optical disk recording methods and optical disk recording apparatuses. More specifically, the present invention relates to an optical disk recording method for recording data on an optical disk including a groove track on which a wobble signal is recorded and a land track having land pre-pits carrying track position information, and an optical disk recording apparatus.
2. Description of the Related Art
An optical disk such as a digital versatile disk-recordable/rewritable (DVD-R/RW) disk generally has, on a recording surface thereof, a groove track on which a wobble signal is recorded and a land track having land pre-pits carrying track position information.
When desired data is written to such an optical disk using an optical disk recording apparatus, an optical pickup reads the wobble signal from the groove track to generate a recording reference clock signal from the wobble signal. The data is written to the optical disk on the basis of the reference clock signal.
In the optical disk recording apparatus, the optical pickup further reads a pre-pit signal from the land track to reproduce, from the pre-pit signal, address/data information having a predetermined phase relationship with the wobble signal. The data is written to the optical disk on the basis of the address/data information.
With the recent progress on high-density optical disks, there has been a tendency to narrow the track pitch between the groove track and the land track. Thus, when a beam is irradiated onto the optical disk from the optical pickup, the phase of the wobble signal is likely to change due to the signal leakage from the adjacent groove track. The influence of the adjacent groove track, which causes such changes in the phase of the wobble signal, is called “crosstalk”.
Since the phase shift induced by crosstalk has an unfixed value but periodically fluctuates in accordance with the shape of the adjacent groove track, it is difficult to cancel the phase shift simply by applying an offset. Due to the phase shift, a recording position may not be located within a standard range when predetermined data is written to the optical disk.
FIG. 12 shows the relationship between a phase comparison reference counter and a pre-pit signal. As shown in FIG. 12, the phase comparison reference counter operates in response to the pre-pit signal. At time t0, a wobble signal is not affected by the influence of crosstalk, and has no phase difference from the pre-pit signal. However, at time t1, the wobble signal is affected by the influence of crosstalk, and has a phase difference from the pre-pit signal.
FIG. 13 shows phase comparison. As shown in FIG. 13, if the recording operation starts at time t0 and ends at time t2, an interval of the recording end position relative to the recording start position corresponds to a period of n channel clocks, which are maximally affected by crosstalk. On the other hand, if the recording operation starts at time t1 and ends at time t2, the wobble signal is maximally affected by crosstalk in the opposite direction at the end of the recording operation in response to the n channel clocks, which are maximally affected by crosstalk, and the maximum phase difference amounts to n×2 channel clocks.
To solve such a problem, a method of feeding back a phase difference between a wobble signal and a pre-pit signal to correct a phase shift of the wobble signal has been proposed (see, for example, Japanese Unexamined Patent Application Publication No. 2005-322407).